Work From Home Day 3

It's the third day working from home and I'm already exhausted. Why is it that I feel so much more tired working from home compared to in the office?

I kept to my hours just like in the office. I don't even have to drive or get stuck in traffic.

So why am I more tired? 

Is it because it's warmer at home? I don't walk as much as in the office? I don't have colleagues to talk to and laugh with? 

I really have no idea.

pearlie